even donald kohn said that the patients should be stopped from coming and kept out.the cdc director acknowledges that some people find the idea terrifying. >> i do understand peoples concerned. the virus is new and different and exotic in some ways and it's truly frightening because it's a terrible disease. but it's a virus that we know how to stop. reporter: the medical missionaries will be tightly isolated unmonitored and the bigger fear could be someone who gets on a plane and then get sick once they land in the united states. if that happens, health officials believe the damage could be quickly contained. >> we have the kind of health care system and the ability to isolate and use the kind of containment that we do that is extremely unlikely and very unlikely that we would even have the condition for there to be an outbreak tour the president played down any potential risks posed in his africa summit next week with hundreds of thousands of people traveling to washington. >> folks coming from these countries would even a marginal risk or an infinitesimal risk, hav